From: ara.t.howard@...
Date: 2005-12-06T10:21:54+09:00
Subject: Re: Problem with method that starts process, yields pid then yields return code

On Tue, 6 Dec 2005, x1 wrote:

> weird thing is, with your first example, the pid prints out before the
> command finishes... where with the second example, nothing is printed
> out until the command exits.

trying putting

   STDOUT.sync = true

at the top of the script.

>
> On 12/5/05, ara.t.howard@noaa.gov <ara.t.howard@noaa.gov> wrote:
>> On Tue, 6 Dec 2005, x1 wrote:
>>
>>> What we have so far works, however ideally, printing the pid should not rely
>>> on the completion of the job. The only thing that should rely on the
>>> completion of the job would be outputting the exitstatus.
>>
>> but that is the exactly the case? example:
>>
>>    harp:~ > ruby servant.rb server &
>>    [2] 31570
>>
>>
>>    harp:~ > ruby servant.rb client
>>    ---
>>    start: "2005-12-05T16:29:21-07:00"
>>    ---
>>    pid: 31572
>>    ---
>>    after getting pid...: "2005-12-05T16:29:21-07:00"
>>    ---
>>    exitstatus: 43
>>    ---
>>    finish: "2005-12-05T16:29:24-07:00"
>>
>>
>> note the times.  __only__ getting the exitstatus relies on job completion (by
>> definition) and is a blocking operation.
>>
>> before i read more of your post make sure you understand the above.  the code
>> again:
>>
>>    harp:~ > cat servant.rb
>>    #! /usr/bin/env ruby
>>    %w( thread drb socket time yaml ).each{|lib| require lib}
>>    class Execute
>>      %w( cmd queue pipe pid thread exitstatus alive ).each{|a| attr_accessor a}
>>      def initialize(cmd)
>>        @cmd = cmd
>>        @queue = Queue.new
>>        @thread = Thread.new(queue) do |q|
>>          pipe = IO.popen(cmd)
>>          q.push pipe
>>          q.push pipe.pid
>>          begin
>>            loop{ stdout = pipe.gets or break }
>>            pipe.close
>>            q.push $?.exitstatus
>>          rescue => e
>>            q.push e
>>          end
>>        end
>>        @pipe = queue.pop
>>        @pid = queue.pop
>>        @exitstatus = nil
>>      end
>>      def wait
>>        @exitstatus = @queue.pop
>>      end
>>    end
>>    class Executioner
>>      def execute cmd
>>        Execute::new cmd
>>      end
>>    end
>>
>>    mode, hostname, port = ARGV.shift, Socket.gethostname, 4501
>>
>>    case mode
>>      when %r/server/i
>>        DRb.start_service "druby://#{ hostname }:#{ port }", Executioner.new
>>        DRb.thread.join
>>
>>      when %r/client/i
>>        DRb.start_service
>>        executioner = DRbObject.new nil, "druby://#{ hostname }:#{ port }"
>>        sleep = executioner.execute "ruby -e' sleep 3 and exit 43 '"
>>        y "start" => Time::now.iso8601
>>        y "pid" => sleep.pid
>>        y "after getting pid..." => Time::now.iso8601
>>        y "exitstatus" => sleep.wait
>>        y "finish" => Time::now.iso8601
>>    end
>>
>>
>> regarding your questions about 'initialize' and 'new' - ruby is object
>> orientied.  everything is an object constructed from a class.  the method new,
>> when called on a class returns an object which was created an initialized
>> using it's initialize method.  check out the 'pickaxe' and the 'ruby way' for
>> deep insight into ruby - you can't code without them.
>>
>> kind regards.
>>
>> -a
>> --
>> ===============================================================================
>> | ara [dot] t [dot] howard [at] noaa [dot] gov
>> | all happiness comes from the desire for others to be happy.  all misery
>> | comes from the desire for oneself to be happy.
>> | -- bodhicaryavatara
>> ===============================================================================
>>
>>
>> cat a.rb
>>
>>
>
>

-a
-- 
===============================================================================
| ara [dot] t [dot] howard [at] noaa [dot] gov
| all happiness comes from the desire for others to be happy.  all misery
| comes from the desire for oneself to be happy.
| -- bodhicaryavatara
===============================================================================